The invention concerns a process for finish-machining the bearing casing of a constant-velocity joint, especially for automobiles, with a spherical bearing surface for the bearing cage and a plurality of guide tracks that basically run axially and interrupt the spherical bearing surface for the bearings transmitting the torques between the bearing casing and the bearing star arranged in the pocket of the bearing cage.
In automobiles with front-wheel drive, the front wheels are driven by joints. Therefore, front-wheel axle shafts must have joints that allow the wheels both to spring in and out, and also to lock. Constant-velocity joints (homokinetic joints) are used to make the wheels drive as steadily as possible. Fixed constant-velocity joints designed as cap joints are used for joints on the front axle shafts, inter alia, while for joints on the rear axle shafts moving constant-velocity joints designed as cap joints are used that allow axial movement in addition to flexure of the joint.
These cap joints are comprised of a bearing star set on the wheel end of the axle shaft, on which the bearing cage with its bearings and the bearing casing connected to the wheel driveshaft sit. On a fixed constant-velocity joint, the bearing casing and star have curved tracks on which the bearings move. On a moving constant-velocity joint, the tracks on the bearing casing and star are designed to be even.
On the constant-velocity joints comprised of a bearing star, bearing cage and bearing casing that are known in practice, the finish-machining of the bearing casing, which has a bearing surface for the cage and guide tracks for the balls, takes a large number of different steps, which are sometimes done on different machines. Starting from a drop-forged bearing-casing blank, in the known finish-machining methods, the guide tracks are produced by broaching and/or milling and final grinding, while the bearing surface is produced by turning. Machining is very expensive, especially finish-machining bearing casings of fixed constant-velocity joints, because both the bearing surface and the guide tracks are designed to be curved in the axial direction of the bearing casing.
The disadvantage of this known production method is that because different machine-tooling methods are used, in which the bearing casing being machined must be transformed many times and potentially fed to different machines, it is very time-consuming and hence expensive to finish-machine the bearing casing. What is more, because of the various transformations, defects occur so that tolerances are only possible within certain limits.
The problem of the invention is to provide a method of finish-machining the bearing casing of a constant-velocity joint so that bearing casings can be finish-machined in a simple, inexpensive way that can be fully automatated with high precision.
The invention solves this problem by producing both the spherical bearing surface for the bearing cage and the guide tracks for the bearings by a turning operation.
This production method in the invention makes it possible, for the first time, to make the bearing casing of a constant-velocity joint by a uniform machine-tooling method, namely a turning operation method, where the turning occurs after the chucking of the blank of a bearing case. As a result of machining only by the turning operation on a machine, the method in the invention has a clear advantage in terms of time, cost and precision over the finish-machining method known in practice.
One practical embodiment of the invention proposes that the axial course of the guide tracks be designed purely spherically.
The invention also proposes that the axial course of the guide tracks be composed of a cylindrical part and a spherical part. Both sorts of bearing casings are used for fixed constant-velocity joints.
The invention also proposes that the guide tracks can run either parallel to the axis or at a sharp angle to the axis of rotation of the bearing casing.
In one practical embodiment of the invention, the tangents of the balls with the accompanying guide tracks run spatially parallel to one another. In particular, the design of the spherical guide tracks also proposes that the distance between the tangents of the balls and the accompanying guide tracks change in the axial direction, which optimizes the transmission of torque.
One special embodiment of the invention proposes that the bearing casing have a polygonal opening on the bottom to connect it to the wheel driveshaft. The design of this polygonal opening for the wheel driveshaft makes it possible to design the bearing casing as a standard component for different constant-velocity joints, since the respective drive can be adjusted via the wheel driveshaft made as a separate component. It is also easier to manufacture a bearing casing without a wheel driveshaft molded onto it. In one advantageous embodiment of this bearing casing, the polygonal opening is designed to be conical in the axial direction. This conicity of the polygonal opening permits self-centering of components being connected to one another.
Lastly, the invention proposes that bearing casing and wheel driveshaft be designed as a one-piece component and the rotary method be a hard rotary method, so that even hardened workpieces can be machined.